(Project) Drawgress Bar — KUAL extension

Dear MobileRead community,
I really miss the old full-scale progress bar. I even wrote feedback to Amazon and asked them to return it. Meanwhile I am waiting for them to take actions, I gathered some thoughts.
I hope for your help! Let's finish this together :)

Goal: to write a KUAL extension that non-intrusively draws full progress bar line with chapter marks (both level 1 and level 2) on each page turn (every-page turn script example is Showtime).
By 'non-intrusive' I mean that it should be more like an overlay written as a script, rather than Java-Bytecode patch.
Hoping that methods of getting book info stay the same, this extension should be compatible with future updates.


Script outline is given below. I only half-finished drawing script, due to lack of experience in bash.
Attached an example of such a progress bar (drawn in fbink manually)



For now I am really stuck with:
— Getting info about current opened book
— Getting pages/locations, chapters info
Where do I even start?
I remember that native booklet is in Java, but I don't know how to extract working values from there.

Attached Thumbnails